Mitsubishi Electric CITY MULTI PUHY-P108 Service Handbook page 198

2. Procedures <PURY>
Follow the procedures below to add or extract refrigerant as necessary depending on the operation mode.
When the function switch switches (SW2-4) on the main board on the outdoor unit are turned to ON, the unit will go into the
refrigerant amount adjust mode.
Operation
not open as fully as it normally does during cooling operation to secure subcooling.
cooling operation.
Notes:
1) There may be cases when the refrigerant amount may seem adequate for a short while after starting the unit in the
refrigerant amount adjust mode but turn out to be inadequate later on (when the refrigerant system stabilizes).
[When the amount of refrigerant is truly adequate.]
The subcooling of BC controller (SC11, SC16) is at or above 5K[9°F], and the SH of the indoor unit is between 5 and
15K[9 and 27°F].
[The refrigerant amount may seem adequate at the moment, but may turn out to be inadequate later on.]
The subcooling of BC controller (SC11, SC16) is below 5K[9°F], or the SH of the indoor unit is below 5K[9°F].
Wait until the subcooling of BC controller reaches 5K[9°F] or above and the SH of the indoor unit is between 5 and
15K[9 and 27°F] to determine that the refrigerant amount is adequate.
SC11: BC controller inlet liquid refrigerant subcool,
SC16: BC controller outlet liquid refrigerant subcool
2) High pressure must be at least 2.0MPa[290psi] to enable a proper adjustment of refrigerant amount to be made.
3) Adjust the refrigerant amount based on the values of TH11 and by following the flow chart below. TH11, SC11, and
SC16 can be displayed by setting the self-diagnosis switch (SW1) on the main board on the outdoor unit.
4) Refrigerant amount adjust mode automatically ends 90 minutes after beginning. When this happens, by turning off
the SW2-4 and turning them back on, the unit will go back into the refrigerant amount adjust mode.
Self-diagnosis swithes on TH11
Self-diagnosis swithes on SC16
Use these switches to figure out the values of TH11, SC11, and SC16.
When the unit is in the refrigerant amount adjust mode, the LEV on the indoor unit does
Control of oil balance, oil recovery, and refrigerant recovery will be disabled only during
Normal operation will be performed during heating only and heating main operations.
1 2 3 4 5 6 7 8 9 10
ON
1 2 3 4 5 6 7 8 9 10
ON
Self-diagnosis swithes on SC11
1 2 3 4 5 6 7 8 9 10
ON
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[ VIII Test Run Mode ]